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In this study, we investigated the effects of nanostructured composite powders (WC-Ni), nickel binder content, and sintering techniques on the morphology and mechanical properties of tungsten carbide. An alternative low-temperature gas-solid reaction route with a short reaction time was employed to produce nanostructured composite powders with 5 and 15 wt% Ni. The powders were consolidated using spark plasma sintering (SPS) and conventional vacuum furnace sintering at temperatures of 1350 °C and 1450 °C. The composite powders were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and particle size measurements. The expansion/contraction of the compacted nanocomposite powders was studied through dilatometric analysis. The composite powders exhibited a uniform distribution of Ni, in both compositions. For the WC-5 wt% Ni nanocomposite powders, the average crystallite sizes for WC and Ni were 41.6 nm and 46.2 nm, respectively. While, for the WC-15 wt% Ni nanocomposite, the crystallite sizes for WC and Ni were 45.6 and 38.4 nm. The sintered composites were evaluated through XRD, SEM, measurements of density and Vickers hardness. The enhanced sinterability of the nanostructured powders enabled their consolidation into (WC-Ni) hard metal with densities approaching the theoretical relative density of 96.07 %, even with low binder content (5 wt% Ni). This is attributed to the uniform distribution of Ni and an extensive Ni-WC interface present prior to sintering. The SPS process at 1350 °C produced sintered bodies (WC-5 wt% Ni and WC-15 wt% Ni) with higher Vickers hardness (2322 HV and 1512 HV, respectively) and superior microstructural quality compared to samples produced by conventional vacuum furnace techniques. These results demonstrated that the mechanical properties of the system WC-Ni processed by SPS are superior to those obtained by vacuum furnace. Therefore, WC-Ni hard metals processed by this approach is a promising alternative to conventional hard metals (WC-Co) for a wide range of applications. [Display omitted] • Impact of the preparation technique on the characteristics of WC-Ni composite powders. • WC-Ni nanocomposite prepared by gas-solid reaction at low temperature and short reaction time. • WC-Ni composites with relative density of 97.67 % and Vickers hardness of 2322 HV. [ABSTRACT FROM AUTHOR]

Corrosion and friction coefficient tests were performed on solid oak wood machined with hard-metal woodworking tools coated with PVD coatings (AlCrN, AlTiN, TiAlN, TiCN and CrN). The tannic acid attacks the carbide more intensively than the PVD coatings. During cutting, corrosion spreads on the cutting edge of the cutter due to mechanical action, which dissolves the cobalt binder of the hard-metal and causes the carbide grains to flake off. After 80 min of contact with the wood, the cobalt content decreases from 3.53 to 1.74%. Depending on the PVD coating material, cracks of 4 to 40 µm in width appear after 120 min (9000 m cutting path). After 120 min of machining, wear, corrosion effects and the influence of corrosion on the coefficients of friction were evaluated for tools with and without PVD coatings. TiCN is the most sensitive to corrosion, while AlCrN and CrN coatings are the least sensitive, with the AlTiN coating being the most affected under real cutting conditions (with mechanical + thermal + corrosion effects) and the tools with CrN and AlCrN coatings being the least affected. Corrosion affects the hard-metal and PVD coatings and reduces the coefficient of friction. The angle between the directions of sliding and sharpening of the cutting edge sharpening significantly influences this parameter. The coefficient of friction of hard-metal WC-Co and PVD coatings is higher in the parallel machining direction than in the perpendicular machining direction and ranges from 16.03% (WC-Co) to 44.8% (AlTiN). The coefficient of friction of hard-metal WC-Co decreases by 5.13% before and after exposure to tannic acid, while the corrosion of PVD coatings reduces it by 4.13% (CrN) to 26.7% (TiAlN). [ABSTRACT FROM AUTHOR]

The research aims to develop a novel and safer milling route to produce Hard Metals. Considering the risks associated with milling fine particles under organic solvents, especially the increased fire and explosion risks, we propose milling under aqueous milling media to diminish the risks associated with fire hazards, while maintaining the oxidation level at a minimum. The samples were sintered in an industrial sintering oven under vacuum at 1380°C subsequent to milling and drying. The characterisation of the materials has been done by X-ray diffraction, scanning electron microscopy, particle size analysis, optical microscopy, and a magnetometer. The obtained results indicate that appropriate properties of the powders after milling and drying as well as the desired biphasic (Co-WC) phases were obtained after sintering, thus proving the feasibility of such a route and diminishing specific fire hazards.

The research aims to develop a novel and safer milling route to produce Hard Metals. Considering the risks associated with milling fine particles under organic solvents, especially the increased fire and explosion risks, we propose milling under aqueous milling media to diminish the risks associated with fire hazards, while maintaining the oxidation level at a minimum. The samples were sintered in an industrial sintering oven under vacuum at 1380°C subsequent to milling and drying. The characterisation of the materials has been done by X-ray diffraction, scanning electron microscopy, particle size analysis, optical microscopy, and a magnetometer. The obtained results indicate that appropriate properties of the powders after milling and drying as well as the desired biphasic (Co-WC) phases were obtained after sintering, thus proving the feasibility of such a route and diminishing specific fire hazards. [ABSTRACT FROM AUTHOR]

The life of cutting tool inserts is critically important for efficient machining, reducing manufacturing cost, embedded energy, and enabling more complex parts to be machined. For these applications, cemented carbide (WC-Co) materials are a prime candidate. The performance of these materials can be limited by early fracture, typically via an intergranular fracture path with respect to carbide grains. This motivates further studies to understand the character of the grain boundary network so that grain boundary engineering (GBE) of WC-Co tools can be used to improve tool life and performance. In this work, we have used Rohrer et al.'s five-parameter grain boundary character distribution (GBCD) analysis to examine the grain boundary network of WC-10wt%Co and WC-10wt%Co-1wt%Cr samples (Rohrer et al., 2004a [ 1 ]). It was found that the measured area fraction of the Σ2 boundaries was comparable to the values reported in the literature despite the relatively larger grain sizes (∼14 μm) and higher cobalt contents. The result suggests that chromium doping increases the area fraction of Σ2 boundaries from 12.8 % to 14.8 %. It is proposed that this is a consequence of altering the Σ2 boundary energy, as associated with adding chromium. • GBCD analysis was conducted on WC-10wt%Co and WC-10wt%Co-1wt%Cr samples. • 1 wt% chromium doping increases the fraction of Σ2 boundaries of WC-10wt%Co. • The increase in area fraction for Σ2 boundaries is approximately 15 %. • This suggests a decrease in grain boundary energy. • This aligns with previous grain boundary mechanical tests. [ABSTRACT FROM AUTHOR]

This work presents the development of a safer processing route for hard metals. Traditional processing of fine particles under organic solvents presents significant explosion risks. The milling under dichloromethane (DCM) reduces the risks associated with fire hazards. After milling and drying, the samples have been sintered in an industrial sintering furnace under a vacuum at 1380°C. The materials’ characterisation has been done by X-ray diffraction, scanning electron microscopy, particle size analysis, optical microscopy, and by magnetic measurements. The present work results reveal the powders’ appropriate properties after milling and drying and the desired biphasic (Co-WC) phases obtained after sintering, thus proving the feasibility of such a route, therefore the diminishing of specific fire hazards.

This paper deals with production of hard metal by powder metallurgy and its effect on the environment. Hard metal is a composite material that consists of tungsten carbide as the hard refractory phase and cobalt or nickel as the soft metal binder phase. It cannot be produced by classical casting technology. Owing to its excellent properties, such as high hardness, wear and heat resistance etc., hard metal can be applied in a variety of industrial fields. Powder metallurgy is a technology for production of a wide range of materials as net-shape products from a compacted and sintered powders mixture. In this paper the impact of all stages of hard metal production by powder metallurgy on the environment is analysed. The presented analysis shows that production of hard metal by powder metallurgy has a minimum effect on the environment.

Due to the great expansion of woodworking, profile tools manufacturing has become current and in demand. In wood industry there are two large groups of tools: rotary and spindle milling cutters that can be profile or flat. The technology of making profile rotary milling cutters requires, apart from cutting, turning, milling, 5-axis grinding operation that is performed on a 5-axis CNC grinding machine with the A'OXYZC configuration.It is a machine of a very complex kinematics and high cost-price. The paper presents a new machine that has been built for 3+2-axis grinding - Profilator 100,used for industrial manufacturing of rotary and spindle profile milling cutters. The accuracy of measures and shapes of the profile cutters built on Profilator 100 is of a high level and in industrial exploitation the difference is not observed between the profile cutters built on 5-axis CNC grinding machines. Regarding technoeconomic cost-effectiveness, production costs of Profilator 100 are lower even by ten times compared to the cost-price of 5-axis CNC grinding machines of renowned world manufacturers such as Schneeberger and Volmer.

The sliding wear and friction behaviour of new developed WC‐stainless steel composites without and with carbon addition were evaluated using a linearly reciprocating sliding tribometer under ball‐on‐flat configuration, sliding against an alumina ball under unlubricated conditions. The wear of both, discs and ball were measured for different applied loads, sliding distances and frequencies. Worn surfaces were investigated by using microscopy and topography techniques. Comparative experiments were performed using flat samples of a conventional WC–Co composite. It was found that the WC–Co grade displayed an undoubtedly better sliding wear resistance and lower coefficient of friction if compared with the newly produced WC‐SS composites. [ABSTRACT FROM AUTHOR]

The frequency and severity of respiratory disorders among workers exposed to hard metal dust is not well known.The objective of this cross-sectional study is to report the prevalence of respiratory symptoms, functional status, and radiological findings in hard metal-exposed workers in Türkiye.Among 139 workers, 96 were machining workers, and 43 were industrial tool sharpening workers. Radiographic abnormalities compatible with pneumoconiosis were found 39% of the workers and were more in machining workers statistically significant.Also, in machining workers group, percentage of expected values of FVC was lower than industrial tool sharpening workers group. The prevalence of respiratory symptoms was 14.3%, and there was not a statistically significant difference in working groups. The study reveals that pulmonary symptoms, functional abnormalities, and radiological findings are mild. Assuming that reversibility may develop with avoidance from exposure when detected at this stage, early diagnosis of lung damage is essential. [ABSTRACT FROM AUTHOR]

This work presents the development of a safer processing route for hard metals. Traditional processing of fine particles under organic solvents presents significant explosion risks. The milling under dichloromethane (DCM) reduces the risks associated with fire hazards. After milling and drying, the samples have been sintered in an industrial sintering furnace under a vacuum at 1380°C. The materials' characterisation has been done by X-ray diffraction, scanning electron microscopy, particle size analysis, optical microscopy, and by magnetic measurements. The present work results reveal the powders' appropriate properties after milling and drying and the desired biphasic (Co-WC) phases obtained after sintering, thus proving the feasibility of such a route, therefore the diminishing of specific fire hazards. [ABSTRACT FROM AUTHOR]

Objectives: Implant-supported restorations are generally used for the replacement of the lost teeth. Stability against masticatory forces and proper retention are critical for optimal durability of restorations. The aim of this experimental study was to compare the retention of cobalt-chromium (Co-Cr) copings made by different techniques. Materials and Methods: Twenty-four solid abutment analogs were mounted and scanned with a desktop scanner. They were divided into two groups (n=12) and received metal copings fabricated by either soft or hard Co-Cr alloy. Soft Cera­mill Sintron Co-Cr patterns were milled and sintered. Hard Co-Cr blocks were milled in a milling machine. The copings were sandblasted, polished, adjusted, and placed on the respective abutments. The frequency of adjustments was recorded for each abutment. The copings were cemented with zinc phosphate cement and underwent tensile test by a universal testing machine. The Mann-Whitney test and t-test were used to compare the two groups (α=0.05). Results: There was no significant difference in retention of copings between the experimental groups. The mean retentive force was 559.58±115.66 N and 557.13 ±130.48 N for the soft and hard metal groups, respectively (P=0.96). Considering the non-normal distribution of adjustment frequency data, the Mann-Whitney test showed that the frequency of adjustments was significantly higher in the hard metal group than the soft metal group (9.5 versus 0.1667; P

Objective: To study the relationship between inhalable dust and cobalt and respiratory symptoms, lung function, exhaled nitric oxide in expired air and CC16 in the Swedish hard metal industry. Methods: Personal sampling of inhalable dust and cobalt, medical examination including blood sampling was performed for 72 workers. Exposure-response relationships was determined using logistic, linear and mixed model analysis. Results: The average inhalable dust and cobalt concentrations were 0.079 and 0.0017 mg/m², respectively. Statistically significant increased serum levels of CC16 were determined when the high and low cumulative exposures for cobalt were compared. Non-significant exposure-response relationships was observed between cross-shift inhalable dust or cobalt exposures and asthma, nose dripping and bronchitis. Conclusions: Our findings suggest an exposure-response relationship between inhalable cumulative cobalt exposure and CC16 levels in blood, which may reflect an injury or a reparation process in the lungs. [ABSTRACT FROM AUTHOR]

The neurotoxicity of hard metal‐based nanoparticles (NPs) remains poorly understood. Here, we deployed the human neuroblastoma cell line SH‐SY5Y differentiated or not into dopaminergic‐ and cholinergic‐like neurons to study the impact of tungsten carbide (WC) NPs, WC NPs sintered with cobalt (Co), or Co NPs versus soluble CoCl2. Co NPs and Co salt triggered a dose‐dependent cytotoxicity with an increase in cytosolic calcium, lipid peroxidation, and depletion of glutathione (GSH). Co NPs and Co salt also suppressed glutathione peroxidase 4 (GPX4) mRNA and protein expression. Co‐exposed cells were rescued by N‐acetylcysteine (NAC), a precursor of GSH, and partially by liproxstatin‐1, an inhibitor of lipid peroxidation. Furthermore, in silico analyses predicted a significant correlation, based on similarities in gene expression profiles, between Co‐containing NPs and Parkinson's disease, and changes in the expression of selected genes were validated by RT‐PCR. Finally, experiments using primary human dopaminergic neurons demonstrated cytotoxicity and GSH depletion in response to Co NPs and CoCl2 with loss of axonal integrity. Overall, these data point to a marked neurotoxic potential of Co‐based but not WC NPs and show that neuronal cell death may occur through a ferroptosis‐like mechanism. [ABSTRACT FROM AUTHOR]

Purpose: The aim of the study was to assess the exposure to Cobalt (Co) and Tungsten (W) in a group of hard metal tool sharpeners through a combined approach of air and biological monitoring, and to evaluate the effectiveness of a control and improvement intervention carried out in collaboration with the medical officers of the local Health Protection Agency, by biomonitoring. Methods: We enrolled 132 workers from 17 companies of the province of Brescia, northern Italy. The study was performed in two phases: (1) an environmental and biomonitoring survey to assess the workers' exposure to Co and W at their usual working conditions; (2) a further biomonitoring survey 3 months after the enforcement of a control and improvement intervention, to assess its effectiveness. Results: Workers were found to be exposed to low concentration of airborne dust containing Co and W but after the intervention we recorded a significant decrease of the urinary concentrations of both Co and W. The extent of the decrease was correlated to the number of preventive industrial hygiene interventions that were carried out. Conclusions: Biological monitoring of Co and W in the hard metal tools manufacturing industry is a sensitive and effective method to evaluate the effectiveness of prevention practices. [ABSTRACT FROM AUTHOR]

Spark plasma sintering is used to consolidate a WC-Co powder produced from milled discharged hard metal cutting inserts. The powder was mixed to 10%wt Co powder and spark plasma sintered (SPS) under 80Mpa pressure, at 1200ºC with heating rate of 160ºC/min. A reference alloy was prepared with a commercial WC powder and 10%wt. Co under the same conditions. The structures of both alloys were investigated by means of scanning electron microscopy and Vickers hardness. The results show structures with densities and hardness at the same level. SPS can be used to produce hard metal pieces directly from scrap powder without any prior chemical and thermal treatment.

Automatic visual inspection methods for product quality checking are spreading more and more in the present 4.0 manufacturing industry. This paper addresses the automatic inspection of edge integrity in accurate holes obtained by direct drilling of cemented carbide with innovative diamond coated tools. These revolutionary cutting tools, recently appeared on the market, can process extremely hard carbide in the sintered state, with massive increase of productivity with respect to standard methodologies like electrical discharge machining (EDM). However, due to the brittleness of the materials, the mechanical cutting process becomes critical and sensitive to tool breakage and workpiece defects generation. In particular, chipping of the hole edges represents one of the most important issues to monitor and take under control. A software procedure, that analyses high-resolution images taken from optical microscopes, was then developed for that aim. Image processing algorithms were designed and applied to enable the automatic extraction of the holes profile, thus permitting the identification and quantification of the leading edge damage in the radial direction. The proposed approach is fully automatic and is based on a profile segmentation that exploits an edge detection algorithm followed by a contour extraction method based on the solution of a partial differential equation. Dedicated metrics were specifically developed to evaluate the extracted profiles. The approach was validated with a factorial plane involving 1.6 mm diameter holes generated with different cutting parameters and tools on tungsten-carbide (WC) material. The technique resulted suitable for the aim, enabling the automatic characterisation of the defects generation phenomenon throughout the entire tools life. This moves a step toward the implementation of both in-line hole inspection procedures and advanced drilling process control. • An automatic algorithm for chipping identification in small holes is proposed. • Innovative diamond drilling tools (φ 1.6 mm) are used on sintered WC. • The hole inspection procedure includes edge detection, extraction and classification. • Chipping phenomenon and connection with cutting process parameters are studied. • The method is compliant with in-process and process control implementations. [ABSTRACT FROM AUTHOR]

The lifetime of WC-Co inserts used in cutting processes, such as milling, is limited by millisecond temperature and mechanical pulses, which occur as a result of interrupted tool-workpiece contact, thermal fatigue and wear. In the current work, synchrotron X-ray diffraction (XRD) was used in conjunction with a pulsed laser heating set-up to characterise the time-dependent development of stresses and microstructure in locally irradiated WC-Co inserts coated by chemical vapour deposition with 6.5 and 3.5 μm thick TiCN and α-Al 2 O 3 films, respectively. Diffraction data from the WC phase were used to evaluate the time and temperature-dependent evolution of in-plane stresses, thermal strains and integral breadths of WC diffraction peaks in experiments with a single and five successive laser shocks applied within 2.2 and 20 s, respectively, using a laser spot diameter of ~5.8 mm and an X-ray beam size of 1 × 1 mm2. The laser heating induces the formation of compressive stresses in the inserts' substrates. Above a temperature of ~750 °C, at the onset of WC-Co composite plastification, compressive stresses relax and then vanish in WC at the maximal applied temperature of ~1300 °C, followed by the build-up of tensile stresses. The applied cyclic heating up and cooling down led to the repetitive formation of compressive and tensile stresses, with temperature dependencies oscillating with the number of applied laser pulses. The observed relatively high tensile stress level of ~1100 MPa in WC was a consequence of the stabilising function of the coating, which hindered the initiation of surface hot cracks and stress relaxation. The stress evolution was coupled with changes in XRD peak broadening, which however strongly depended on the particular hkl reflections and showed oscillatory behaviour within a single temperature cycle. In summary, the unique diffraction set-up revealed stress levels and provides insight into the WC-Co composite plastification mechanism governing the stress build-up and relaxation in locally thermo-shocked WC-Co inserts at millisecond time resolution. Unlabelled Image • In-situ laser heated coated WC-Co cutting inserts were studied by synchrotron XRD. • The complex stress/strain evolution in successive thermal shocks was analysed. • Heating induces compressive stresses up to ~−1300 MPa before WC-Co plastification. • Plastification leads to compressive stress relaxation and tensile stress build-up. • In-plane stresses are hkl -dependent, owing to WC elasto-plastic anisotropy. [ABSTRACT FROM AUTHOR]

Abstract Non-destructive and reliable quality control methods are a key aspect to designing, developing and manufacturing new materials for industrial applications and new technologies. The measurement of the magnetic saturation is one of such methods and it is conventionally employed in the cemented carbides industry. We present a general quantum mechanics based relation between the magnetic saturation and the components of the binder phase of cemented carbides, which can be directly employed as a quality control. To illustrate our results, we calculate the magnetic saturation of a binder phase, 85Ni15Fe binary alloy, using ab-initio methods and compare the theoretical predictions to the magnetic saturation measurements. We also analyse interface and segregation effects on the magnetic saturation by studying the electronic structure of the binder phase. The excellent agreement between calculations and measurements demonstrates the applicability of our method to any binder phase. Since the magnetic saturation is employed to ensure the quality of cemented carbides, the present method allows us to explore new materials for alternative binder phases efficiently. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract Cemented carbides are of great importance for the manufacturing industry. The outstanding properties of high hardness and wear resistance of this material, consisting mainly of tungsten carbide cemented with cobalt (WC-Co), have caused its use in a wide range of applications. The aim of this study is to provide comprehensive and detailed cradle-to-gate life cycle inventory (LCI) data for the typical non-Chinese production of WC-Co, which is assumed to take place in Canada and the United States. Different scenarios are presented regarding recycling rate and a life cycle impact assessment (LCIA) is conducted to illustrate the applicability of the LCI data. The LCI results in this study are of similar magnitude or lower compared to previous studies and indicate that the typical non-Chinese production requires less energy compared to Chinese production. The LCIA results show that the mining, hydrometallurgy and powder metallurgy phases in general dominate the cradle-to-gate life cycle impacts. Most of the impacts are caused by a limited number of inputs and outputs (e.g. kerosene, sulfidic tailings, water use during mining and electricity use), and recycling greatly reduces the impacts. A comparison with Chinese tungsten carbide (WC) powder production showed that the LCIA results in non-Chinese WC production were lower for climate change, photochemical oxidant formation and water depletion, but higher for terrestrial acidification, ozone depletion and freshwater eutrophication. The LCI data and the LCIA results for non-Chinese production can subsequently be used in product-specific cradle-to-grave life cycle assessments involving WC-Co or any of its precursors. Highlights • Ready-to-use cradle-to-gate inventory data for cemented carbides (WC-Co). • A few inputs and outputs dominate life cycle environmental impacts. • Recycling greatly reduce life cycle environmental impacts of WC-Co. • Typical non-Chinese production requires less energy than Chinese production. [ABSTRACT FROM AUTHOR]

Andrea L Armstead,1,2 Bingyun Li1–3 1Department of Orthopaedics, School of Medicine, 2School of Pharmacy, West Virginia University, 3Mary Babb Randolph Cancer Center, Morgantown, WV, USA Abstract: As the number of commercial and consumer products containing engineered nanomaterials (ENMs) continually rises, the increased use and production of these ENMs presents an important toxicological concern. Although ENMs offer a number of advantages over traditional materials, their extremely small size and associated characteristics may also greatly enhance their toxic potentials. ENM exposure can occur in various consumer and industrial settings through inhalation, ingestion, or dermal routes. Although the importance of accurate ENM characterization, effective dosage metrics, and selection of appropriate cell or animal-based models are universally agreed upon as important factors in ENM research, at present, there is no “standardized” approach used to assess ENM toxicity in the research community. Of particular interest is occupational exposure to tungsten carbide cobalt (WC-Co) “dusts,” composed of nano- and micro-sized particles, in hard metal manufacturing facilities and mining and drilling industries. Inhalation of WC-Co dust is known to cause “hard metal lung disease” and an increased risk of lung cancer; however, the mechanisms underlying WC-Co toxicity, the inflammatory disease state and progression to cancer are poorly understood. Herein, a discussion of ENM toxicity is followed by a review of the known literature regarding the effects of WC-Co particle exposure. The risk of WC-Co exposure in occupational settings and the updates of in vitro and in vivo studies of both micro- and nano-WC-Co particles are discussed. Keywords: engineered nanomaterial, occupational exposure, lung disease, cancer, toxicity, particle

Mechanical Seal use highly efficient alternative water having a great quantity of an aqueous solution and has an advantage no corrosion brine. Metal Carbide composites have been investigated as potential materials for high temperature structural applications and for application in the processing industry. The existing Mechanical seal material is a highly expensive carbide alloy, and it is difficult to take a price advantage. Therefore the study of replacing body area with inexpensive steel material excluding O-ring and contact area which demands high characteristics is needed.

Abstract This paper presents a new approach on the wet attrition of some composite WC-10Co powders by using an aqueous medium instead of the classical organic solvent based processing method. The hard metal powders have been characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), laser particle size analysis (PSA), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis coupled with mass spectrometry (TG-MS). The XRD investigation revealed that no significant changes in the structure of the material occur during milling, while the SEM and PSA analysis highlighted the presence of agglomerates that are formed during the drying of the aqueously processed powders. The observed composite flakes are formed by the sequential cold-welding and fracturing process of the particles. The elemental powders were blended and milled together in an aqueous media (distilled water + corrosion inhibitor) in order to achieve a homogeneous dispersion of the constituents. Prolonged milled durations are resulting in an incremental oxidation process, leading to the formation of CoO(OH). XPS analyses revealed that Co oxidises in depth, as opposed to the sample obtained by classical route, which reveals only superficial oxide. The residual moisture evidenced by TG-MS could also favour the formation of agglomeration and oxide in the powder. [ABSTRACT FROM AUTHOR]

Background: It is well known that hard metal workers have historically been affected by contact allergy to cobalt. Knowledge is sparse about occupational skin exposure to cobalt, in terms of skin doses and sources of exposure, which could be used to improve protection of workers. Objectives: To improve knowledge about skin doses and sources of skin exposure to cobalt within hard metal production, thereby facilitating better protection of workers. Methods: Forty workers were sampled on the index finger by acid wipe sampling after 2 hours of work. The samples were analysed with inductively coupled plasma mass spectrometry. Cobalt spot testing was performed in the work environment. Results: The highest skin doses were found among raw material workers. Skin doses among other production workers were also significant. Most office workers had low, but measurable, levels of cobalt on the skin. Glove use varied between workers. Cobalt was found on production equipment, on items in the canteen area, and on handles and buttons throughout the company. Conclusions: Cobalt skin doses were prominent, and originated from contact with raw materials, sintered materials, and contaminated surfaces. Cobalt was present on surfaces outside production areas. Companies need to identify and reduce skin exposure for protection of workers. [ABSTRACT FROM AUTHOR]

Apart by vacancies, the different pseudo-cubic phases NbC, Nb 4 C 3 and Nb 6 C 5 , can accommodate any stoichiometry of NbC x (0.75 ≤ x ≤ 1.0) in the binary phase diagram and enable a large process window. Properties, like micro-hardness, hot hardness, sliding wear resistance, elastic modulus and toughness can be tailored by the C/Nb ratio, the addition of secondary carbides and the type of binder. SPS sintered and cobalt bonded (NbC 0.88 -12Co SPS). NbC and Nb 2 O 5 have so far no REACH classifications related to human toxicology and are not listed as substances of very high concern contrary to Co 3 O 4 . The NiMo-bonded stoichiometric NbC 1.0 grades enable the substitution of cobalt by nickel, SPS by conventional sintering and NbC 0.88 by NbC 1.0 in view of functional properties. Nickel bonded NbC grades have improved toughness versus cobalt bonded NbC grades, but loosed in hardness. NiMo and NiMo 2 C bonded NbC 1.0 grades in combination with secondary carbides compensated the loss in hardness while keeping the toughness. The tool lifes of uncoated NbC 1.0 -12Ni4Mo4VC and NbC 0.88 -12Co under dry turning of 42CrMo4 and C45E were between +30% to +200% higher and up compared to WC-6Co (extra fine grain). Niobium is today largely available as resource. NbC grades displayed lower dry sliding friction over WC grades. The softer Ni- and NiMo-bonded NbC 1.0 -grades have a higher dry abrasive wear resistance (ASTM G65 ), even with lower toughnesses, as the tougher WC-Co grades. [ABSTRACT FROM AUTHOR]

Aqueous suspensions of hard metal powders and their use are known to have significant environmental and economic advantages over the systems employed nowadays using organic solvents. The present research describes developing a novel and less harmful processing route for hard metal production. Aqueous spray drying is convenient for obtaining dried WC-Co granules without extensive agglomeration. The spray-dried powders exhibit good flowability due to their shape and relatively narrow particle size distribution. The spray-dried granules have been pressed and sintered in an industrial sintering oven under a vacuum. The characterisation of the samples has highlighted the size, morphology, and some technological properties, while the sample's metallurgical properties have been assessed for the sintered compacts. By employing the abovementioned processes, both the granules and the subsequent hard metals revealed appropriate properties with biphasic (Co-WC) sintered compacts, which prove that such a process is feasible. [Display omitted] • The granules' properties can be controlled by employing different spray-drying temperatures. • The evaporation rate mainly influences the morphology and size of the granules. • High inlet temperature and relatively high binder content produce hollow spheres and doughnut shape granules. • Hydrogen debinding before sintering promotes a more uniform microstructure. • Partial vacuum (Argon) debinding leads to Co-rich areas, grain growth and some porosity to the different carbon balance. [ABSTRACT FROM AUTHOR]